1. Field of the Invention
The present invention relates to an X-ray generator for generating X-rays from an anticathode by causing electrons generated from a cathode to impinge upon the anticathode.
2. Description of the Related Art
The above-mentioned X-ray generator is a device for generating X-rays which are irradiated to a sample to be analyzed in an X-ray diffraction device, for example. The device disclosed in Japanese Laid-open Patent Publication No. 2003-014895 (Patent Citation 1 ), is known as an example of this type of X-ray generator. As shown in FIG. 7, this X-ray generator has an electron gun 52 which houses a filament 51 as the cathode, and a rotating anode 53 which is provided opposite the filament 51. The electron gun 52 is formed in the shape of a flat rectangular solid, as shown in the partial magnified view of FIG. 7A. An electron gun in the shape of a flat rectangular solid is also disclosed in Japanese Laid-open Patent Publication No. 2007-115553 (Patent Citation 2 ), for example.
A housing 54 that gives the electron gun 52 the rectangular solid shape thereof also serves as a conductive Wehnelt electrode. An aperture 55 as a region for passing the electrons generated from the filament 51 is provided to the conductive Wehnelt electrode in the portion opposite the filament 51. The electron gun 52 and the rotating anode 53 are provided inside a casing 57. The inside of the casing 57 is kept hermetically sealed in a vacuum state.
The casing 57 is grounded, the filament 51 has a potential of −60 kV, for example, and the Wehnelt electrode 54 has a potential several hundred volts different from the filament 51. Electrons (thermo electrons) generated from the filament 51 as a result of applying electrical power impinge upon a surface of the rotating anode 53 at the high voltage described above. The region on which the electrons impinge in this manner is an X-ray focal point F. X-rays R0 are generated from this X-ray focal point F. The X-rays R0 are extracted to the outside via an X-ray extraction window 56 formed of beryllium or the like in an appropriate location of the wall of the casing 57.